OOM conditions

[Martin Dengler]

On Fri, Nov 06, 2009 at 04:50:53PM +0000, Tomeu Vizoso wrote:
> On Wed, Nov 4, 2009 at 14:16, Martin Dengler <martin at martindengler.com> wrote:
> > On Fri, Oct 30, 2009 at 11:22:13PM +0100, Tomeu Vizoso wrote:
> >> On Fri, Oct 30, 2009 at 16:58, Richard A. Smith <richard at laptop.org> wrote:
> >> > Working the table at the Boston book festival I was reminded how
> >> > painful the OOM stuff is on a gen 1. The demo machines were in
> >> > this state a lot as each visitor would open up a new
> >> > program.  Basically you have to just turn the unit off and restart
> >> > as trying to recover is futile.
> >>
> >> What if activities had a higher oom_score? Would that protect enough
> >> the processes that once killed require a system restart (X, shell,
> >> etc)?
> >
> > See patch vs sugar-toolkit HEAD below[1] (I can backport to 0.82 if
> > wanted).
> 
> Maybe would be better to have the shell do that? So it works for
> non-python activities.

Patch inline below.

> >> Regards,
> >>
> >> Tomeu
> >
> > Martin
> >
> Thanks,
> 
> Tomeu

Martin


(untested) patch against
http://cgit.sugarlabs.org/sugar-toolkit/mainline/tree/src/sugar/activity/activityfactory.py
:

From 4bd6fb9f7f245c2aed92d6964746627d0c96cbec Mon Sep 17 00:00:00 2001
From: Martin Dengler <martin at martindengler.com>
Date: Sat, 7 Nov 2009 10:55:16 +0000
Subject: [PATCH] sacrifice activities to the OOM killer first

change the OOM-killer score of launched activities to be the maximum.
See discussion at http://linux-mm.org/OOM_Killer
---
 src/sugar/activity/activityfactory.py |   35 +++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/src/sugar/activity/activityfactory.py b/src/sugar/activity/activityfactory.py
index ee0fd92..5deee6e 100644
--- a/src/sugar/activity/activityfactory.py
+++ b/src/sugar/activity/activityfactory.py
@@ -65,6 +65,39 @@ def _close_fds():
             pass
 
 
+def __oom_adj_pid(pid, omm_adj_value=None):
+    """ Change a process' OOM likelihood to oom_adj_value.
+
+    By default, use the value of gconf path
+    "/desktop/sugar/performance/oom_adj_default"; if none exists, make
+    this process most likely to be killed (oom_adj_value=15).
+
+    Linux-specific.  See http://linux-mm.org/OOM_Killer for details.
+    """
+    oom_adj_fullpath = "/proc/%s/oom_adj" % pid
+    if os.path.exists(oom_adj_fullpath):
+        try:
+
+            # get values/defaults from gconf
+            import gconf
+            gconf_dir = "/desktop/sugar/performance"
+            gconf_key = "oom_adj_default"
+            client = gconf.client_get_default()
+            if not client.dir_exists(gconf_dir):
+                client.add_dir(gconf_dir, gconf.CLIENT_PRELOAD_NONE)
+            if oom_adj_value is None:
+                oom_adj_value = client.get_int(gconf_dir + "/" + gconf_key)
+                if oom_adj_value is None:
+                    oom_adj_value = 15
+                    client.set_int(gconf_dir + "/" + gconf_key,
+                                   oom_adj_value)
+
+            file(oom_adj_fullpath).write(oom_adj_value)
+
+        except:
+            pass
+
+
 def create_activity_id():
     """Generate a new, unique ID for this activity"""
     pservice = presenceservice.get_instance()
@@ -276,6 +309,8 @@ class ActivityCreationHandler(gobject.GObject):
             stdout=log_file.fileno(),
             stderr=log_file.fileno())
 
+        __oom_adj_pid(child.pid)
+
         gobject.child_watch_add(child.pid,
                                 _child_watch_cb,
                                 (environment_dir, log_file))
-- 
1.6.2.5

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